The present invention concerns a hydraulic dashpot for motor vehicles, with a shock-absorbing piston that accommodates bypasses that can be alternatingly opened and closed.
Adapting the performance of a motor-vehicle hydraulic dashpot to external driving conditions by re-adjusting it while the vehicle is in operation is known. This function is ensured in one such known dashpot by providing the piston with both hydraulically controlled constrictions and alternatingly open and closed bypasses.
Both DE 3 518 327 C2 and DE 4 020 045 C1 disclose such a hydraulic dashpot. These devices, however, have a drawback in that the hydraulic fluid can flow very rapidly, especially along the controlling edges of the valve""s plunger, when a narrow bypass opens and there is a wide difference in pressure between the hydraulics chambers. The result is excessively high hydraulic forces that in the extreme case can impair the accuracy of the plunger""s alternating action. It has often been attempted to combat this problem by controlling several bypasses with a single solenoid valve or by a bypass maintained constantly open by a solenoid. Alternative solutions involve either revolving regulators or several solenoid valves, although they usually occupy too much space.
The object of the present invention is an advanced hydraulic dashpot wherein the disruptive effects that occur due to the constantly varying forces exerted by the fluid when its flow through the bypasses is controlled or diverted will be decreased.
The present invention has several advantages. First, the means of selecting and of varying the width of the bypasses are very simple and compact. Furthermore, the means are very insensitive to hydraulic influence.